The present invention relates to digital imagery.
Traditional illustration media usually have texture, which refers to a characteristic visual and tactile quality of a particular medium. Paper, for example, has texture in the form of ridges formed by interlocking fibers. Similarly, canvas has texture in the form of ridges formed by interwoven fibers.
The texture of most media exhibits some degree of random variation in at least some aspects. For example, the ridges present in paper vary in aspects such as orientation, location, size, and shape. Even the ridges formed by the interwoven fibers of canvas, which are typically oriented in a same general direction, can exhibit random variation in aspects such as size, color, and shape. Media having texture, whether random or not, will be referred to in this specification as textured media.
A mark is an impression left on a medium as a result of an instance of an application of a marking tool, such as a pencil or paint brush. A mark can be as simple as a dot, spot, or stamp resulting from a quick touch of the tool to the surface of the medium. A mark can also be a line that results from the movement of the tool across the medium while the tool is in contact with the medium. Marking on textured medium usually produces a mark that derives at least some texture from the textured medium. A watercolor mark, for example, usually derives texture from the paper on which the mark is made because the watercolor pigment used to make the mark conforms to and bleeds into the texture of the paper. In addition to deriving texture from the medium on which it was made, a mark may also derive texture from the marking medium, such as pigment, being used. For example, a mark made with oil paint, which is a type of pigment, can develop texture when the oil paint dries and cracks. A mark having texture, such as one that derives texture from textured media, will be referred to in this specification as a textured mark.
A system for generating digital imagery can model and render images of marks in response to user input specifying the marks. Additionally, the system can render an image that shows an accumulation of the specified marks. An image that shows an accumulation of marks specified by a user input will be referred to in this specification as a final image.
One way the system models and renders an image of a mark is to define a stroke that is a representation of the mark. Such systems define a stroke as a sequence of tips delimited by a starting point and an ending point of the stroke. A tip is a representation of a stamp of a marking tool and, furthermore, has an outline that corresponds to the outline of the stamp. For example, a tip representing a stamp made by a pencil is a dot. The outline of the tip, in this example, is a circle. A stroke can include information that specifies an appearance of the mark, such as but not limited to position, opacity, and color information.